Purification and refinement of magnesium and magnesium alloys



Patented Jan. 12, 1937 PATENT OFFICE PURIFICATION AND REFINEMENT OF MAG- NESIUM MAGNESIUM ALLOYS Alexander Luschenowsky, Berlin, Germany No Drawing. Application October 16, 1935,

Serial No. 45,311. In Germany July -7, 1933 6 Claims.

Applications have been filed in Germany on July '7, 1933, and July 24, 1935; and in Czechoslovakia on'February 16, 1934.

The present invention relates to processes for the purification and refinement of magnesium and magnesium alloys.

The properties of magnesium and magnesium alloys are unfavourably influenced by the presence of impurities, particularly by the presence 10 of metal chlorides and nitrides.

It is already known to purify magnesium and its alloys by passing hydrogen (H) through the metal whilst it is in a molten state. It is likewise known for the purpose of purifying magnesium and magnesium alloys to introduce steam into the molten mass of metal. Furthermore, the employment of inert gases and of hydrogen in a moist condition is also known.

When the'aforesaid known processes are employed the purification does not take place sufficiently vigorously and requires a considerable time. It is, however, advantageous to make the time required for purification as short as possible in order to lessen the danger of formation of compounds of the magnesium with the constituents of the air. If, however, the time for purification is reduced, the known processes do not sufiiciently ensure that the harmful substances, metal chlorides, nitrides and the like, are removed from the magnesium or its alloys'to a sufficient extent for the production of a. metal capable of resisting corrosion. It is only necessary for the metal to contain a very small amount of impurities of the aforesaid kind in order to cause the magnesium or magnesium alloys to become decomposed or destroyed, particularly on contact with water or with moist air.

According to the present invention it is proposed to provide a. process for the purification and o refinement of magnesium and magnesium alloys consisting primarily in treating the magnesium or magnesium alloys, whilst they are in the molten state, with hydrogen peroxide (H202); The hydrogen peroxide is, according to the invention,

passed through the molten metal either alone or in conjunction with hydrogen.

Such a. treatment of the molten metal with hydrogen peroxide or with hydrogen peroxide and hydrogen efl'ects a reliable purification of the magnesium and its alloys in an astonishingly short time, the molten mass being, during the operation,, practically entirely freed from all the substances which are to be removed (chlorine I compounds and also, in particular, nitrogen com- 5 pounds of magnesium). Magnesium or a magnesium alloy purified or refined according to the aforesaid new process exhibits a higher resistance to corrosion as also better mechanical properties, and a lower degree of inflammability.

One preferred method of carrying out the in- 5 vention is given by way of example below:

A solution of hydrogen peroxide in water (for example a solution having a concentration of 2 to 15%) is heated in a closed vessel up to a temperature below its boiling point. The hydrogen 10 peroxide gas which is evolved is conveyed by means of a conduit to the magnesium or magnesium alloy, which has been melted up in the usual manner with a suitable flux. During this operation the aforesaid conduit is gradually immersed l5 deeper and deeper in the molten mass and thereby agitates the latter. The treatment of the molten mass with hydrogen peroxide may, according to the invention, also be efiected in conjunction with the employment of hydrogen. In this case the hydrogen is passed through the aqueous solution of hydrogen peroxide and after becoming charged with hydrogen peroxide is led into the molten metal in similar manner to that above set forth.

The process according to the invention can be carried out in open crucibles without any gas protection. The gas rising through the molten mass becomes ignited and burns above the surface of the metal.

The purification takes place very rapidly. For example, with a crucible containing 5 kg. of magnesium, the time required is about one minute. The surface of the purified molten mass is as bright as a mirror. After the purification the molten mass is allowed to stand for a few min- 35 utes, whereupon the metal can be cast into moulds without protection against gas or other screening protection.

Iclaim:

1. A process for the purification and refinement of magnesium and magnesium alloys consisting in treating the said magnesium and magnesium alloys in the molten state with hydrogen peroxide 2. A process for the purification and refinement of magnesium and magnesium alloys consisting in treating the said magnesium and magnesium alloys in the molten state with hydrogen charged with hydrogen peroxide.

3. A process for the purificationand refinement of magnesium and magnesium alloys consisting in treating the said magnesium and magnesium alloys in the molten state with hydrogen peroxide and its decomposition products respectively given ofi from an aqueous solution of hydrogen peroxide.

4. A process for the purification and refinement of'magnesium and magnesium alloys, consisting in passing hydrogen through an aqueous solution of hydrogen peroxide and then into the metal whilst the latter is me. molten state.

5. A process for the refinement and purification of magnesium and magnesium alloys, comprising in steps: causing vapours to be given ofi from a 2% to 15 heated aqueous solution of hydrogen peroxide; and gassing said vapours-into the magnesium and magnesium alloys whilst 

